Ubuntu 12.04. I could not convert to Nginx and keep ISPconfig3 and my production server up. All I really wanted was PHP FPM. I got that the Apache worker model as a bonus. It's stable. It's beautiful. Unfortunately, my webmail no longer works. I knew squirrel mail will not work because it depends on libraries that are removed by MPM worker but round cube should work. Any ideas on getting this to work? See: 162.243.246.138/roundcube/
All php based software that you install with apt requires mod_php on Debian and Ubuntu, by changing the worker model you disable these packages. To get them working again you will have to write a new apache config file for them that uses e.g. php-fpm or php-fcgi. Btw. php-fpm is supported by all perfect server setups out of the box, so there is no need to switch the apache worker model for that.